Work Energy and Power

Practice Questions:

Question 31: moderate

A body of mass 2 kg collides with a massless spring of force constant K = 4 N/m. The spring compresses by 1m. If coefficient of friction between the body and the surface is 0.1, the speed of the body at the time of collision is :

1. 2 m/s

2. 4 m/s

3. 6 m/s

4. 0.5 m/s

View Answer

The Kinetic Energy of the object will go to increase potential energy of the spring and a part of energy will be lost to friction

U1= ½ K x²= ½ × 4× 1² = 2J

Work done against friction = ü.mg.x= 0.1× 20 × 1= 2 J

So total kinetic energy is 4 = ½× 2 ×v ² ⇒ v = 2 m/s

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Question 32: moderate

A particle is placed at the origin and a force F = kx is acting on it (where k is positive constant). If U(0) = 0, the graph of U(x) versus x will be (where U is the potential energy function) :